1. Field of the Invention
The invention relates to a fuel injection improved fuel injection valve for internal combustion engines.
2. Description of the Prior Art
In a fuel injection valves of this type, a piston-shaped valve member is guided so that it can move axially in a bore of a valve body, wherein the end of the valve member oriented toward the combustion chamber has a valve sealing face, which it uses to cooperate with a stationary valve seat provided on the end of the bore oriented toward the combustion chamber in order to control the through flow of fuel to an injection opening that feeds into the combustion chamber of the internal combustion engine. The opening stroke motion of the valve member occurs in opposition to a restoring force, usually the force of a valve spring, by means of a high injection pressure of the incoming fuel that acts on the valve member in the opening direction.
In order to introduce the force of this opening pressure onto the valve member, the valve member has a pressure shoulder that is constituted by an annular step, which protrudes into a pressure chamber formed by means of a cross sectional widening of the bore. With its cross sectionally enlarged shaft part remote from the combustion chamber, the valve member is guided so that it can slide in a sealed fashion in a part of the bore in the valve body which acts as a guide section. This guide section of the valve member thus constitutes a guide surface at the end of the valve member remote from the combustion chamber, which is subjected to a high degree of wear due to its very snug guidance in the bore. Therefore the known fuel injection valves, particularly at very high injection pressures, have the disadvantage that fuel pressure fields build up inside the valve member guide, which transmit one-sided lateral forces onto the valve member and thus, through a one-sided contact of the valve member, cause a one-sided surface pressure between the valve member and the bore guide surface, which leads to a more intense wear that can result in undesired leakage and the destruction of the injection valve.
The German utility model DE 295 04 608 discloses a fuel injection valve for internal combustion engines in which the guide surface between the valve member and the guide bore in the valve body is divided into two separate guide regions. This should prevent a one-sided contact of the valve member against the wall of the guide bore and consequently a one-sided wear. However, the known fuel injection valve has the disadvantage that as a result of the large clearance between the surfaces of the valve member and the guide bore wall between the separate guide regions, a tearing of a lubrication film between the moving components can occur, which once more encourages wear.